10 Cervical Disk Disease • Disk disease is often described as a result of two pathologies: – Disk herniation characterized by herniated nucleus pulposus (HNP). – Degenerative disk disease (DDD). • These conditions are common and commonly asymptomatic: – 10% of asymptomatic individuals younger than 40 years have HNP on magnetic resonance imaging (MRI). – 25% of asymptomatic individuals younger than 40 years have DDD on MRI. • The progression of a pathologic intervertebral disk may result in compression of adjacent neural structures including the spinal cord and neural roots. • HNP: – Secondary to stress on annulus of disk: ∘ Most often posterolateral as the supportive posterior longitudinal ligament (PLL) is weakest here. – Increased risk for herniation from aging and disk degeneration: ∘ Decreased water content and proteoglycan content of nucleus pulposus. – Characteristics of herniation: ∘ Protrusion: ▪ Base (neck) wider than head of herniation. ▪ Herniation of nuclear pulposus penetrates through annular fibers but remains within the annular margin. ∘ Extrusion: ▪ Base narrower than head of herniation. ▪ Herniation tears through annular margin. ▪ Can displace (migrate) cranially or caudally. ∘ Sequestration: ▪ Free disk fragment separated from original herniation. • DDD (spondylosis): – Aging of disk results in biochemical component changes (Fig. 10.1): ∘ Decreased cross-linking of collagen, decreased water content. ∘ Decreased blood supply to outer annulus: ▪ Lactate increases with resultant acidic changes, further degenerating disk. Fig. 10.1 Thompson disk degeneration staging (I–V). (a) Cadaveric examples of disk degeneration with associated (b) magnetic resonance imaging for each stage. Note grade I exemplifies characteristics of a healthy disk with appropriate disk height and high water content. Grade V illustrated by significant disk height loss, loss of water content, and bony sclerosis and osteophytes. – Decreased strength from degenerative changes leads to chronic tears throughout annulus. – Degenerative cycle includes the following: ∘ Disk degeneration (disk bulging, decreased disk space). ∘ Joint degeneration (facet arthrosis and uncinate spurring). ∘ Ligamentous alterations (ligamentum flavum thickening due to loss of disk height). ∘ Spinal deformity (kyphosis, following the loss of disk height and transfer of load to the uncovertebral and facet joints). • Both DDD and HNP result in tearing of disks with eventual impingement of nearby neural elements including spinal cord. • Axial neck pain: – Unclear etiology. – Peripheral disk contains nociceptors and PLL: ∘ Annular tears and herniation potentially activates these receptors. • Radiculopathy:
10.1 Background
10.2 Etiology and Pathophysiology
10.3 Symptoms and Clinical findings (Table 10.1)
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